I'm a amateur photographer and I am trying to get a portfolio together of nightclub photography.

I have a Nikon D40 and so far have been quite successful in taking 'clean' photographs around clubs but one thing i cant get the hang of is how to produce photos like this.

www.pbase.com/davos/image/97187332.jpg

This is from the 'nightclub photography' thread on the forums. The advice is to set the flash to rear sync, have the iso 200-250, appiture 4-5.6 exposure 1s or 1/80s

My trouble is if im shooting as low as 1s, the subject will be blurred. And even though my flash is set to rear sync, its the built in flash, not a hotshoe flash so im guessing that will have a major effect too. Obviously the only way to stop the blur is to increase shutter speed but then i loose some of the colours from the lights.

Any advice on how to achieve pictures like this? I thought maybe a speedlight would help or maybe im looking in the wrong direction here, but as i know nothing about speedlights I thought id be best off asking for some advice.

Thanks in advance! Carl.